Polymer alloy of an ethylene-tetrafluoroethylene copolymer

ABSTRACT

A polymer alloy comprising ETFE having a melting point of at most 250° C. and a melt flow rate of at least 20 at 297° C., PPS and a compatibilizer (such as 3-aminopropyltriethoxysilane).

TECHNICAL FIELD

The present invention relates to a polymer alloy comprising anethylene-tetrafluoroethylene copolymer (hereinafter referred to asETFE), a polyphenylene sulfide (hereinafter referred to as PPS) and acompatibilizer.

BACKGROUND ART

ETFE is excellent in heat resistance, flame retardancy, chemicalresistance, weather resistance, a low friction property and a lowdielectric characteristic, and is used in a wide range of fields, suchas coating materials for heat resistant flame retarding electric wires,corrosion resistant piping materials for chemical plants, agriculturalvinyl house materials, and release coating materials for kitchenutensils. However, since the intermolecular cohesion is weak, theaffinity to other materials is poor, and there has been a problem suchthat a polymer alloy having excellent properties can hardly be obtained.

In order to improve the compatibility of the fluorine-containingcopolymer and a polyolefin, a method of using a polyolefin as alkylacrylate-modified (JP-B-4-73459), or a method of incorporating carboxylgroups, hydroxyl groups or epoxy groups to a fluorine-containing polymer(JP-A-62-57448), has been proposed.

The former is effective in a case where the fluorine-containing polymeris a vinylidene fluoride type polymer or a vinyl fluoride type polymerhaving a high polarity, but in the case of ETFE having a low polarity,the compatibility can not be improved.

Whereas, the latter may, for example, be (1) a method wherein afluorine-containing polymer and a non-fluorine type thermoplasticpolymer having functional groups are blended, (2) a method wherein, inthe synthesis of a fluorine-containing polymer, polymer units based onthe polymerization of a polymerizable monomer having a functional group,are incorporated, (3) a method wherein the reactive groups present in afluorine-containing polymer are reacted with a compound having afunctional group or a compound capable of forming a functional group bythe reaction, or (4) a method wherein a fluorine-containing polymer ismodified by e.g. oxidation, hydrolysis or thermal decomposition.

However, with respect to ETFE, the above method (1) is not effective,since, as mentioned above, the fluorine-containing polymer and thenon-fluorine type thermoplastic polymer having a functional group, haveno compatibility. The above method (2) is expensive and not practical,since the monomer useful for the copolymerization reaction is verylimited. The above method (3) can not be adopted since thefluorine-containing polymer usually has no reactive group. In the abovemethod (4), the fluorine-containing polymer is so stable that it isimpossible to form carboxyl groups, hydroxyl groups or epoxy groups bye.g. oxidation, hydrolysis or thermal decomposition.

On the other hand, a thermoplastic composition obtained by blending afluorine-containing polymer, PPS and an aminoalkoxysilane, has beenproposed (JP-A-8-53592). This composition has a part of mechanicalproperties improved, but it is not disclosed and unclear whether it isin a form of a polymer alloy having a good dispersed state. Further,with respect to ETFE, it is disclosed to use Afron COP C-88A grade inExamples. However, the present inventors have found that from ETFE ofsuch a grade and PPS, it is impossible to obtain a polymer alloy havingstable mechanical properties in a good dispersed state even in thepresence of an aminoalkoxysilane.

DISCLOSURE OF THE INVENTION

The present invention provides a polymer alloy having good mechanicalproperties, wherein ETFE and PPS are microscopically uniformlydispersed.

BEST MODE FOR CARRYING OUT THE INVENTION

The present inventors have firstly found a compatibilizer effective forETFE by lowering the melting point of ETFE and lowering the degree ofcrystallinity and secondly found it possible to increase the melt-mixingproperty of ETFE and PPS by increasing the melt flow rate of ETFE at297° C. (hereinafter "a melt flow rate at 297° C." will be referred toas "MFR") to lower the viscosity (the molecular weight) and thereby tominimize the viscosity difference from PPS which usually has a lowmolecular weight and low viscosity, and from the foregoing two aspects,have found it possible to obtain a good polymer alloy wherein ETFE andPPS are microscopically dispersed, and thus have arrived at the presentinvention.

Namely, the present invention is a polymer alloy comprising (a) anethylene-tetrafluoroethylene copolymer having a melting point of at most250° C. and a melt flow rate of at least 20 at 297° C., (b) apolyphenylene sulfide, and (c) a compatibilizer.

For ETFE to be used in the present invention, it is preferred tocopolymerize a small amount of a third monomer in addition to ethyleneand tetrafluoroethylene. As the third monomer, a compound having nohydrogen atom in a polymerizable unsaturated group, or a compound havinghydrogen atoms in a polymerizable unsaturated group, may be employed.

As the compound having no hydrogen atom in a polymerizable unsaturatedgroup, hexafluoropropylene or a perfluoro(alkylvinyl ether) may, forexample, be mentioned. As the compound having hydrogen atoms in apolymerizable unsaturated group, an olefin such as propylene, 1-buteneor 2-butene, a fluorine-containing olefin such as vinylidene fluoride or(perfluorobutyl)ethylene, a vinyl ether such as an alkylvinyl ether or afluoroalkylvinyl ether, or a (meth)acrylate such as a fluoroalkylmethacrylate or a fluoroalkyl acrylate, may, for example, be mentioned.

As ETFE, one having a melting point of at most 250° C. and a MFR of atleast 20, is used. ETFE is preferably one having a melting point of atmost 235° C. and a MFR of at least 20, or one having a melting point ofat most 250° C. and a MFR of at least 30, more preferably one having amelting point of at most 235° C. and a MFR of at least 30.

As a method for lowering the melting point, the reaction ratio ofethylene to tetrafluoroethylene (amount of ethylene reacted/amount oftetrafluoroethylene reacted) may be departed from 1 (molar ratio), sothat the alternating nature is lowered, and the degree of crystallinityis lowered, or polymerization units based on a third monomer areincreased to lower the degree of crystallinity, or by using both ofthem, the melting point can be made to be at most 250° C.

Specifically, the amount of ethylene reacted/amount oftetrafluoroethylene reacted, is preferably at most 0.82 (molar ratio),more preferably at most 0.75 (molar ratio) and at least 0.25 (molarratio). Further, the polymer units based on (perfluorobutyl)ethylene asa third monomer, are made preferably to be at least 2 mol %, morepreferably at least 3 mol % and at most 30 mol %, in ETFE, whereby themelting point can be made to be at most 250° C.

With respect to MFR, the molecular weight of ETFE may be lowered toincrease MFR to a level of at least 20, by a method carried out in ausual radical polymerization, such as by increasing the molecular weightcontrolling agent during the polymerization, by increasing the amount ofthe initiator, or by reducing the monomer pressure.

PPS to be used in the present invention is a polymer containing at least70 mol %, preferably at least 80 mol %, of a repeating unit of thestructural formula [--C₆ H₄ --S--] (wherein --C₆ H₄ -- is a phenylenegroup). If the above repeating unit is less than 70 mol %, thecrystallinity as a characteristic of a crystalline polymer, tends to below, and the inherent physical properties of PPS tend to be impaired,such being undesirable.

PPS is generally known to be one having a linear molecular structure(linear type) having no branched or crosslinked structure, one having amolecular structure having a branched or crosslinked structure to someextent (half linear type) or one having a molecular structure having ahigh density of branched or crosslinked structures (crosslinked type),depending upon the process for its production. One having a suitablemolecular structure is used for molding depending upon the particularpurpose of use.

With PPS, the viscosity changes to a large extent depending upon thepolymerization method. The viscosity of PPS formed by polymerization,i.e. a so-called viscosity upon polymerization, is usually at a level offrom 1000 to 2000 poise at 300° C. in the case of linear type PPS, at alevel of from 200 to 600 poise in the case of the half linear type PPS,and at a level of at most 100 poise in the case of the crosslinked typePPS.

Among these, the half linear type PPS and the crosslinked type PPS areused for molding after increasing their molecular weights by a meanssuch as heat treatment after the polymerization to bring theirviscosities to a level of from 1000 to 2000 poise at 300° C. In thepresent invention, PPS of any structure can be used, but one having aviscosity upon polymerization of at least 200 poise at 300° C. ispreferred, although the reason is not clearly understood. Within thisviscosity range, PPS of a linear type or a half linear type isparticularly preferred.

The viscosity of PPS to be used for molding, i.e. the viscosity uponpolymerization with respect to the linear type PPS or the viscosityafter heat treatment with respect to the half linear type andcrosslinked type PPS, is not particularly limited so long as a moldedproduct can be obtained, but from the viewpoint of toughness of PPSitself, one having a viscosity of at least 100 poise at 300° C. ispreferred, and from moldability, one having at most 10000 poise ispreferred.

The compatibilizer to be used in the present invention is one which hascompatibility with ETFE and compatibility or reactivity with PPS andwhich is capable of performing compatibilizing effects during the meltmixing of ETFE and PPS and has heat resistance. A preferredcompatibilizer is an organo hydrolyzable silane having a reactivefunctional group, which is reactive with PPS. As the organo hydrolyzablesilane, an organo alkoxysilane having an amino group or an epoxy groupas the reactive functional group, is preferred. Particularly preferredis an organo alkoxysilane having an amino group.

Specific examples of the organo alkoxysilane include3-aminopropyltriethoxysilane,N-(2-aminoethyl)-3-aminopropyltrimethoxysilane,N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane,3-glycidyloxypropyltrimethoxysilane, 3-ureidepropyltriethoxysilane,N-phenyl-3-aminopropyltrimethoxysilane,N-allyl-3-aminopropyltrimethoxysilane and2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane.

The blend proportions of ETFE and PPS being within a range of from 5/95to 95/5, are preferred in order to obtain a polymer alloy havingexcellent properties. The blend amount of the compatibilizer ispreferably from 0.1 to 10 wt %, particularly preferably from 0.3 to 5 wt%, relative to the sum of ETFE and PPS.

The polymer alloy of the present invention is uniformly dispersed tosuch an extent that dispersed particles can not be ascertained byobservation by means of a scanning electron microscope, i.e. in a statewhere the average dispersed particle size is at most 1 μm, and hasexcellent mechanical properties.

The polymer alloy of the present invention can be used as a moldingmaterial for production of various molded products. To the polymeralloy, various fillers such as inorganic powder, glass fibers, carbonfibers, metal oxides and carbon, may be incorporated in a range not toimpair the performance. Further, other than the fillers, pigments,ultraviolet absorbers or any other optional additives may be mixed asthe case required.

Methods for measuring the physical properties and characteristics of thepolymer alloy are as follows.

Dispersed state: Observed by a scanning electron microscope with 720magnifications.

MFR: In accordance with a test method of ASTM D3159, 5 g of a sample wasextruded at 297° C. under a load of 5 kg from a nozzle having a diediameter of 2 mm and a die length of 8 mm, and the weight of the sampleextruded for 15 seconds, was calculated to a value corresponding to theamount extruded for 10 minutes (g/10 min).

Melting point: The heat absorption peak by DSC was measured at atemperature raising rate of 10° C./min.

Viscosity: By a kouka-type flow tester, 1.5 g of a sample was extrudedat 300° C. under a load of 20 kg from a nozzle having a die diameter of1 mm and a die length of 10 mm, and the viscosity was calculated fromthe extruded volume flow rate Q (ml/sec).

Flexural strength: In accordance with ASTM D790.

Tensile elongation: In accordance with ASTM D638.

Izod impact strength: In accordance with ASTM D256.

Now, the present invention will be described in further detail withreference to Examples (Examples 1, 2 and 8 to 10) and ComparativeExamples (Examples 3 to 7 and 11). However, the present invention is byno means restricted thereto.

EXAMPLE 1

79 wt % of PPS (PPS having a viscosity of 1160 poise at 300° C. obtainedby heat treatment of PPS of a half linear type having a viscosity, uponpolymerization, of 300 poise at 300° C.), 20 wt % of ETFE-1 having amelting point of 230° C. and a MFR of 45 and 1 wt % of3-aminopropyltriethoxysilane, were dry-blended and then kneaded andextruded at an extrusion temperature of 330° C. by means of a twin screwextruder, to obtain pellets. The obtained pellets were injection-moldedat an injection temperature of 320° C. at a mold temperature of 140° C.to obtain a molded specimen. The dispersed state of the broken surfaceof the molded specimen was observed by an electron microscope, wherebyno dispersed particles were ascertained, and the average dispersedparticle size was at most 1 μm. The results of measurements ofmechanical properties of the molded specimen are shown in Table 1.

EXAMPLES 2 to 7

Tests were carried out in the same manner as in Example 1 by using,instead of ETFE-1 used in Example 1, ETFE-2 having a melting point of230° C. and a MFR 25 in Example 2, ETFE (Afron COP C-88A, manufacturedby Asahi Glass, melting point: 267° C., MFR: 12) in Example 3, ETFE(Afron COP C-88AX, manufactured by Asahi Glass, melting point: 260° C.,MFR: 11) in Example 4, ETFE (Afron COP C-88AXX, manufactured by AsahiGlass, melting point: 256° C., MFR: 10) in Example 5, ETFE (Afron COPC-88AM, manufactured by Asahi Glass, melting point: 260° C., MFR: 36) inExample 6, and ETFE-3 having a melting point of 230° C. and a MFR of 14in Example 7. The results are shown in Table 1.

EXAMPLE 8

A test was carried out in the same manner as in Example 1 by usinglinear type PPS (PPS having a viscosity, upon polymerization, of 1250poise at 300° C.) instead of PPS used in Example 1. The averagedispersed particle size of dispersed particles of the molded specimen,and the results of measurements of the mechanical properties, are shownin Table 1.

EXAMPLE 9

A test was carried out in the same manner as in Example 1 using the sameamount of 3-glycidyloxypropyltrimethoxysilane instead of3-amiopropyltriethoxysilane used in Example 1. The average dispersedparticle size of dispersed particles of the molded specimen and theresults of measurements of the mechanical properties, are shown in Table1.

EXAMPLE 10

A test was carried out in the same manner by changing PPS, ETFE-1 andthe compatibilizer used in Example 1 to 59 wt % of PPS, 40 wt % ofETFE-1 and 1 wt % of the compatibilizer. The average dispersed particlesize of dispersed particles of the molded specimen and the results ofmeasurements of the mechanical properties, are shown in Table 1.

EXAMPLE 11

A test was carried out without using a compatibilizer and changing PPSand ETFE-1 used in Example 1 to 80 wt % of PPS and 20 wt % of ETFE-1.The average dispersed particle size of dispersed particles of the moldedspecimen and the results of measurements of the mechanical properties,are shown in Table 1.

                                      TABLE 1                                     __________________________________________________________________________               Average         Izod impact                                           dispersed Flexural Tensile strength                                           particle strength elongation (kg · cm/cm.sup.2)                   Examples                                                                            ETFE size  (kg/mm.sup.2)                                                                      (%)  Notched                                                                           Not notched                                    __________________________________________________________________________    1     ETFE-1                                                                             <1 μm                                                                            15.1 10.5 3.2 Non-                                                   destructive                                                             2 ETFE-2 <1 μm 14.8 10.0  3.3 Non-                                               destructive                                                             3 C-88A  5 μm 13.1 4.0 2.1 60.7                                            4 C-88AX  7 μm 12.9 4.0 1.6 60.2                                           5 C-88AXX  2 μm 12.6 6.2 1.6 Non-                                                destructive                                                             6 C-88AM  5 μm 13.1 4.2 1.4 35.3                                           7 ETFE-3  1.4 μm 12.3 4.1 2.3 40.7                                         8 ETFE-1 <1 μm 16.2 11.5  3.5 Non-                                               destructive                                                             9 ETFE-1 <1 μm 14.5 9.8 3.0 Non-                                                 destructive                                                             10  ETFE-1 <1 μm  9.0 12.4  3.1 Non-                                             destructive                                                             11  ETFE-1 8 μm 10.2 3.2 1.2 10.3                                        __________________________________________________________________________

Industrial Applicability

By using ETFE having a melting point of at most 250° C. and a MFR of atleast 20, it is possible to obtain a polymer alloy having goodmechanical properties, wherein ETFE and PPS are microscopicallydispersed.

What is claimed is:
 1. A polymer alloy comprising (a) anethylene-tetrafluoroethylene copolymer having a melting point of at most235° C. and a melt flow rate of at least 20 g/10 min at 297° C. by ASTMD3159, (b) a polyphenylene sulfide, and (c) a compatibilizer.
 2. Thepolymer alloy according to claim 1, wherein the compatibilizer is anorgano hydrolyzable silane having a reactive functional group.
 3. Thepolymer alloy according to claim 2, wherein the reactive functionalgroup is an amino group or an epoxy group.
 4. The polymer alloyaccording to claim 1, wherein the viscosity of the polyphenylene sulfideupon polymerization is at least 200 poise at 300° C.
 5. The polymeralloy according to claim 1, wherein the proportions of theethylene-tetrafluoroethylene copolymer and the polyphenylene sulfide arefrom 5/95 to 95/5 (by weight ratio).
 6. The polymer alloy according toclaim 5, wherein the compatibilizer is an organo hydrolyzable silanehaving a reactive functional group.
 7. The polymer alloy according toclaim 6, wherein the reactive functional group is an amino group or anepoxy group.
 8. The polymer alloy according to claim 5, wherein theviscosity of the polyphenylene sulfide upon polymerization is at least200 poise at 300° C.
 9. The polymer alloy according to claim 1, whereinthe proportion of the compatibilizer is from 0.1 to 10 wt % relative tothe sum of the ethylene-tetrafluoroethylene copolymer and thepolyphenylene sulfide.
 10. The polymer alloy according to claim 9,wherein the compatibilizer is an organo hydrolyzable silane having areactive functional group.
 11. The polymer alloy according to claim 10,wherein the reactive functional group is an amino group or an epoxygroup.
 12. The polymer alloy according to claim 9, wherein the viscosityof the polyphenylene sulfide upon polymerization is at least 200 poiseat 300° C.
 13. The polymer alloy according to claim 9, wherein theproportions of the ethylene-tetrafluoroethylene copolymer and thepolyphenylene sulfide are from 5/95 to 95/5 (by weight ratio).
 14. Thepolymer alloy according to claim 1, wherein the melting point of theethylene-tetrafluoroethylene copolymer is at most 235° C., and the meltflow rate is at least 30 g/10 min. at 297° C.
 15. The polymer alloyaccording to claim 14, wherein the compatibilizer is an organohydrolyzable silane having an amino group or an epoxy group.
 16. Thepolymer alloy according to claim 15, wherein the proportions of theethylene-tetrafluoroethylene copolymer and the polyphenylene sulfide arefrom 5/95 to 95/5 (by weight ratio).
 17. The polymer alloy according toclaim 1, wherein the proportion of the compatibilizer is from 0.3 to 5wt % relative to the sum of the ethylene-tetrafluoroethylene copolymerand the polyphenylene sulfide.
 18. The polymer alloy according to claim14, wherein the proportion of the compatibilizer is from 0.3 to 5 wt %relative to the sum of the ethylene-tetrafluoroethylene copolymer andthe polyphenylene sulfide.